Heavy oils are generally referred to those hydrocarbon comprising oils with high viscosity or API gravity less than about 20. Crude oils and crude oil residuum obtained after atmospheric or vacuum distillation of crude oils that exhibit an API gravity less than about 20 are examples of heavy oils. Upgrading of heavy oils is important in production, transportation and refining operations. An upgraded heavy oil typically will have a higher API gravity and lower viscosity compared to the heavy oil that is not subjected to upgrading. Lower viscosity will enable easier transportation of the oil. A commonly practiced method for heavy oil upgrading is thermal treatment of heavy oil. Thermal treatment includes processes such as visbreaking and hydro-visbreaking (visbreaking with hydrogen addition).
Primary limitations in thermal treatment of heavy oils, such as visbreaking, are the formation of toluene insolubles (TI) at high process severities and reactor fouling. Fouling of the reactor vessel results in down time as well as energy losses. The instant invention addresses the fouling limitation of thermal treatment, such as visbreaking and presents a method for improved operability of a heavy oil thermal treatment facility.